Re: [PATCH RFC V2 17/37] arm/virt/acpi: Build CPUs AML with CPU Hotplug support

[Gavin Shan]

Hi Salil,

On 9/26/23 20:04, Salil Mehta wrote:
> Support of vCPU Hotplug requires sequence of ACPI handshakes between Qemu and
> Guest kernel when a vCPU is plugged or unplugged. Most of the AML code to
> support these handshakes already exists. This AML need to be build during VM
> init for ARM architecture as well if the GED support exists.
>
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> ---
>   hw/arm/virt-acpi-build.c | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 6b674231c2..d27df5030e 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -858,7 +858,18 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, 
> VirtMachineState *vms)
>        * the RTC ACPI device at all when using UEFI.
>        */
>       scope = aml_scope("\\_SB");
> -    acpi_dsdt_add_cpus(scope, vms);
> +    /* if GED is enabled then cpus AML shall be added as part build_cpus_aml */
> +    if (vms->acpi_dev) {
> +        CPUHotplugFeatures opts = {
> +             .acpi_1_compatible = false,
> +             .has_legacy_cphp = false
> +        };
> +
> +        build_cpus_aml(scope, ms, opts, memmap[VIRT_CPUHP_ACPI].base,
> +                       "\\_SB", NULL, AML_SYSTEM_MEMORY);
> +    } else {
> +        acpi_dsdt_add_cpus(scope, vms);
> +    }
>       acpi_dsdt_add_uart(scope, &memmap[VIRT_UART],
>                          (irqmap[VIRT_UART] + ARM_SPI_BASE));
>       if (vmc->acpi_expose_flash) {

I don't think it's enough to check vms->acpi_dev. vCPU hotplug needn't to be
supported even vms->acpi_dev exists. For example when vGICv2 instead of
vGICv3 is enabled, and so on.

Thanks,
Gavin